Add DOM primitives (dom-set-prop, dom-call-method, dom-post-message), bump SW cache v2, remove video demo

New platform_js primitives for direct DOM property/method access and
cross-origin iframe communication. Service worker static cache bumped
to v2 to flush stale assets. Removed experimental video embed from
header island, routes, and home page.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sx/sx/docs-content.sx

@@ -2,9 +2,7 @@
 
 (defcomp ~sx-home-content ()
   (div :id "main-content" :class "max-w-3xl mx-auto px-4 py-6"
-    (~doc-code :code (highlight (component-source "~sx-header") "lisp"))
-    (~doc-code :code (highlight (component-source "~video-player") "lisp"))
-    (~doc-code :code (highlight (component-source "~video-embed") "lisp"))))
+    (~doc-code :code (highlight (component-source "~sx-header") "lisp"))))
 
 (defcomp ~docs-introduction-content ()
   (~doc-page :title "Introduction"

sx/sx/layouts.sx

@@ -32,7 +32,7 @@
           (span :style (str (display "block") (mb 2)
                             (cssx (:text (colour "violet" 699) (size "4xl") (weight "bold") (family "mono"))))
             "(<sx>)")))
-      ;; Tagline — NOT in anchor. Clicking "reactive" cycles colour + fetches video.
+      ;; Tagline — clicking "reactive" cycles colour.
       (p :style (str (mb 1) (cssx (:text (colour "stone" 500) (size "lg"))))
         "Framework free "
         (span
@@ -42,15 +42,7 @@
           :on-click (fn (e)
             (batch (fn ()
               (swap! idx inc)
-              (reset! shade (+ 400 (* (mod (* (deref idx) 137) 5) 50)))))
-            ;; Only fetch video if none loaded (marsh: reactive + conditional hypermedia)
-            (let ((embed (dom-query-by-id "video-embed")))
-              (when (not (dom-get-prop embed "firstChild"))
-                (dom-dispatch (dom-get-prop e "currentTarget") "fetch-video" {}))))
-          :sx-get "/api/random-video"
-          :sx-target "#video-embed"
-          :sx-swap "innerHTML"
-          :sx-trigger "fetch-video"
+              (reset! shade (+ 400 (* (mod (* (deref idx) 137) 5) 50))))))
           "reactive")
         " hypermedia")
       ;; Lake: server morphs copyright on navigation without disturbing signals.
@@ -62,12 +54,6 @@
                               "margin-left:0.5em;")
               (str "· " path))))))))
 
-;; Video player island — defisland so the morph algorithm preserves it across
-;; navigations. Content swapped in via sx-get from the reactive word click.
-;; Empty initially (zero height). Iframe provides height when loaded.
-(defisland ~video-player ()
-  (div :id "video-embed"
-       :style "position:relative;width:20rem;max-width:66vw;"))
 
 ;; @css grid grid-cols-3
 
@@ -147,11 +133,6 @@
              :style (str "opacity:" (+ (* (/ 1 depth) 0.75) 0.25) ";"
                          "transition:opacity 0.3s;")
           (~sx-header :path (or path "/")))
-        ;; Video island — preserved across navigation morphs (like ~sx-header).
-        ;; Outside logo-opacity so it doesn't fade.
-        ;; Marsh demo: reactive click triggers hypermedia fetch, result lands here.
-        ;; Island renders as inline <span>; force it to block so margin:auto centers.
-        (div :style "display:flex;justify-content:center;" (~video-player))
         ;; Sibling arrows for EVERY level in the trail
         ;; Trail row i is level (i+2) of depth — opacity = (i+2)/depth
         ;; Last row (leaf) gets is-leaf for larger current page title